Device for guiding variable pitch diffuser vanes of a turbine engine

ABSTRACT

A device for guiding variable pitch diffuser vanes of a turbine engine is provided. The device includes a first ring having an axial portion at its periphery that is extended by a collar extending radially outwards; a second ring mounted around the axial portion of the first ring so as to cooperate therewith to define a plurality of outwardly open sockets; a plurality of cylindrical bushings, each mounted in a respective socket for the purpose of receiving a guide pivot of a diffuser vane; and a resilient clamping ring for cooperating with one of the rings in order to clamp the two rings axially one against the other.

BACKGROUND OF THE INVENTION

The invention relates to the general field of turbine enginecompressors, in particular for an airplane turboprop or turbojet. Moreprecisely, the invention relates to a device enabling variable pitchdiffuser vanes of a compressor stage to be guided.

The high pressure compressor of an aviation turbine engine has aplurality of diffuser stages with variable pitch vanes that alternatewith stages of rotor blades. The diffuser vanes serve to modify the flowcharacteristics of the gas depending on the operating speeds of theturbine engine.

Each variable pitch diffuser vane has a control pivot at its head and aguide pivot at its foot, the control pivot passing through a statorjacket (known as the casing) of the turbine engine and co-operating witha control member for varying the pitch of the vanes, while the guidepivot is pivotally mounted in a bushing received in a socket in an innerring of the turbine engine. By acting on the control member, it is thuspossible to vary the pitch of the vanes in the stage in question.

The compressor casing is generally made as two half-shells in order tofacilitate assembly. However, in order to reduce weight and increase theperformance of the assembly, proposals have been made to make the casingas a single piece (extending over 360°). Unfortunately, when thecompressor casing is a single piece in the tangential direction, it isfound to be considerably more complicated to install the variousportions of the compressor inside it. In particular, having recourse toa casing made of two half-shells enables the stator elements of thecompressor to be assembled individually and then to be put in placearound the elements of the rotor. With a single-piece casing, it isnecessary to assemble in alternation a rotor stage and then a statorstage.

Furthermore, in order to dimension the rotor line of the compressor, itsshroud line needs to be as close as possible to the flow passage for thestream of gas passing therethrough. This has the consequence of reducingthe space available under the passage, and thus of making it necessaryto reduce the radial size of the device for guiding the diffuser vanes.

Document FR 2 875 270 describes a diffuser vane guide device in whichthe inner ring under the vanes is made up of two half-rings clampedtogether by axial keys, a sealing member support being mounted on theinner ring. With such a device, the spacing between the vane guidepivots must be sufficient to enable the keys to be received thereinwithout giving rise to cracks. Furthermore, that device presentsrelatively large radial size.

OBJECT AND SUMMARY OF THE INVENTION

A main object of the present invention is thus to propose a device forguiding variable pitch diffuser vanes that does not have such drawbacks.

In accordance with the invention, this object is achieved by a devicefor guiding variable pitch diffuser vanes of a turbine engine, thedevice comprising a first ring having an axial portion at its peripherythat is extended by a collar extending radially outwards, a second ringmounted around the axial portion of the first ring so as to co-operatetherewith to define a plurality of outwardly open sockets, a pluralityof cylindrical bushings, each mounted in a respective socket for thepurpose of receiving a guide pivot of a diffuser vane, and a resilientclamping ring for co-operating with one of the rings in order to clampthe two rings axially one against the other.

The first and second rings of the device of the invention form an innerring that may be a single piece in the tangential direction (i.e.extending over 360°). Together, these two rings define a plurality ofoutwardly open sockets that receive the support bushings for the guidepivots of the diffuser vanes. These two rings are held one against theother by clamping. As a result, the device of the invention enables thediffuser vanes to be installed easily on an inner ring that may extendover 360°. In addition, having recourse to a clamping ring for holdingthe two rings together makes it possible to avoid any cracks forming andenables the radial size of the assembly to be reduced.

Preferably, the first ring has a plurality of angular cutouts in itsaxial portion in order to pass radial teeth carried by the clampingring. The teeth of the clamping ring exert a force clamping the tworings one against the other.

The teeth of the clamping ring may extend radially outwards and thesecond ring may have a side face with a profile that slopes radially.Under such circumstances, the clamping ring is designed initially to beretracted in order to pass inside the first ring, and then to bereleased in order to enable the teeth to pass radially through thecutouts in the first ring and bear radially against the sloping sideface of the second ring so as to exert an axial force clamping the tworings one against the other.

Alternatively, the teeth of the clamping ring may extend radiallyinwards, the cutouts in the first ring may each have a profile thatslopes radially, and the second ring may have an inwardly open annulargroove. Under such circumstances, the clamping ring is designedinitially to be opened up to be received completely within the groove inthe second ring, and then to be released in order to enable the teeth topass radially through the cutouts in the first ring and block the secondring axially in position so as to exert an axial force clamping the tworings one against the other.

The clamping ring may be an open ring or a spiral ring. The first ringand the second ring may include indentations for receiving the bushings.

The invention also provides a turbine engine compressor having at leastone device as defined above. The invention also provides a turbineengine including such a compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the present invention appearfrom the following description made with reference to the accompanyingdrawings that show embodiments having no limiting character. In thefigures:

FIG. 1 is a diagrammatic view of a compressor diffuser stage having avane guide device in an embodiment of the invention;

FIG. 2 is a perspective view of the clamping ring of the FIG. 1 device;

FIG. 3 is an exploded perspective view of the FIG. 1 device;

FIG. 4 is a diagrammatic view of a guide device in another embodiment ofthe invention;

FIG. 5 is a perspective view of the clamping ring of the FIG. 4 device;

FIG. 6 is a perspective view of the clamping ring in another embodimentof the invention; and

FIG. 7 is a perspective view of the clamping ring in another embodimentof the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a diagram showing a diffuser stage 2 of an aviation turbineengine compressor, e.g. a high pressure compressor of an airplaneturboprop or turbojet. Such a diffuser stage is located upstream from astage of rotor blades (not shown) of the compressor.

The diffuser stage 2 has a plurality of stator vanes 4 of variable pitchangle that are arranged in the flow passage 6 for the stream of gaspassing through the compressor.

Each variable pitch vane 4 is in the form of an airfoil 8 terminating ata radially outer end (or vane head) by a control pivot 10 (or top pivot)and at a radially inner end (or vane foot) by a guide pivot 12 (orbottom pivot).

The control pivot 10 of the vane 4 passes through a jacket 14 of theturbine engine casing and co-operates with a control member for varyingthe pitch of the vanes. For this purpose, the control pivot is typicallyterminated by a head 16 on which there is engaged one end of a controllink 18 having its other end co-operating with a control ring 20.

The control links 18 and the control ring 20 form the member forcontrolling the pitch of the vanes 4. Turning the control ring about thelongitudinal axis of the turbine engine serves to cause the controllinks to turn and thus to modify simultaneously the pitch of all of thevariable pitch vanes in the high pressure compressor stage.

Each guide pivot 12 is for turning inside a hollow cylindrical bushing22 forming a pivoting support. These bushings 22 are housed inindentations 24 a, 24 b formed in an inner ring of the turbine engine,the bushings and the indentations being substantially complementary inshape.

More precisely, and in accordance with the invention, the inner ringreceiving the bushings 22 of the pivot for guiding the diffuser vanescomprise an upstream ring 26, a downstream ring 28, and a resilientclamping ring 30 (see also FIGS. 2 and 3).

The upstream ring 26 presents an axial portion 32 at its inner peripherythat is extended upstream by a collar 34 extending radially outwards.The collar 34 has a plurality of indentations 24 a of shapecomplementary to a portion of the bushings 22. This upstream ring 26 maybe made as a single piece, i.e. it may form a single ring extendingaround 360°.

The downstream ring 28 is mounted around the axial portion 32 of theupstream ring 26 and it is axially spaced apart therefrom so as toco-operate therewith to form a plurality of cylindrical sockets 36 thatare outwardly open and that are to receive the bushings 22. Like theupstream ring, this downstream ring 28 may be a single piece.

Furthermore, in an upstream side face, the downstream ring presents aplurality of indentations 24 b of shape complementary to a portion ofthe bushings 22. Thus, the bushings 22 receiving the guide pivots of thediffuser vanes are positioned in the sockets 36 defined between theupstream and downstream rings and they are held circumferentiallytherein by the indentations 24 a, 24 b.

As shown in FIG. 2, the clamping ring 30 is a resilient ring that isopen or split. This clamping ring 30 has teeth 38 that are regularlyspaced apart around an axis of revolution X-X of said clamping ring, theteeth extending radially outwards.

Furthermore, these teeth 38 of the clamping ring are for passingradially through angular cutouts 40 formed in the axial portion 32 ofthe upstream ring 26 so as to clamp the two rings 26 and 28 axially oneagainst the other as can be understood from the process for assemblingthe diffuser stage, as described below.

Initially, the bushings 22 are positioned on the guide pivot 12 of thevanes 4. The upstream ring 26 is mounted so as to put the indentations24 a made in its downstream side face into correspondence with thebushings 22. Then the downstream ring 28 is docked axially fromdownstream going upstream so as to put the indentations 24 b formed inits upstream side face into correspondence with the bushings 22.

The clamping ring 30 is then put into position via the inside of theupstream ring. For this purpose, and since it is made of resilientmaterial, the clamping ring is retracted (e.g. by means of anappropriate tool) in order to reduce its diameter so as to enable it topass into the upstream ring. The teeth 38 carried on the clamping ringare angularly positioned in register with the cutouts 40 made in theupstream ring.

The clamping ring is then released, thereby enabling it to return to itsinitial diameter. Its teeth 38 then pass radially (from the insidetowards the outside) through the cutouts 40 in the upstream ring 26 soas to come into radial abutment against the downstream side face of thedownstream ring 28.

This downstream side face of the downstream ring presents a profile 42that slopes radially (i.e. a profile that lies on a plane that slopesdownstream). The teeth 38 of the clamping ring are chamfered with thesame radial slope such that the clamping ring can be used either wayround (upstream or downstream). Thus, as represented by the arrows inFIG. 1, when the teeth of the clamping ring come radially into contactagainst the downstream side face of the downstream ring, they apply anaxial force from downstream to upstream against the downstream ring,thereby causing the upstream and downstream rings to be clamped axiallyone against the other.

FIGS. 4 and 5 show a guide device in another embodiment of theinvention.

This embodiment differs from the above-described embodiment inparticular in terms of the downstream ring 28′ and of the resilientclamping ring 30′. In particular, the downstream ring 28′ has an annulargroove 44 that is open towards the inside and that is dimensioned so asto be capable of receiving the clamping ring 30′ in full.

As shown in FIG. 5, the clamping ring 30′ has teeth 38′ that areregularly distributed around its axis of revolution X-X and that extendradially inwards. As in the above-described embodiment, these teeth 38′are for passing radially through angular cutouts 40 formed in the axialportion 32 of the upstream ring 26 (but in this example from the outsidetowards the inside) so as to provide axial clamping of the upstream anddownstream rings 26 and 28′ one against the other.

In this example, the assembly process is as follows. Initially, thebushings 22 are positioned on the guide pivots 12 of the vanes. Thedownstream ring 28′ is axially docked from downstream to upstream so asto put its indentations 24 b into correspondence with the bushings 22.The clamping ring 30′ is then opened up (e.g. using an appropriate tool)in order to increase its diameter and it is positioned entirely(including its teeth 38′) in the groove 44 formed in the downstream ring28′, as shown in chain-dotted lines in FIG. 4.

The clamping ring 30′ is held in this state and in this position inorder to enable the upstream ring 26 to dock axially (from upstream todownstream) so as to put its indentations 24 a into correspondence withthe bushings 22. The teeth 38′ of the clamping ring are angularlypositioned so as to face the cutouts 40 formed in the upstream ring.

The clamping ring is then released, thereby enabling it to return to itsinitial diameter. Its teeth 38′ then pass radially (from outside towardsthe inside) through the cutouts 40 in the upstream ring 26 so as to comeradially into abutment against downstream side faces of the cutouts 40in the upstream ring.

A downstream side face of a cutout 40 presents a profile 46 with aradial slope (i.e. it lies in a plane sloping downstream). The teeth 38′of the clamping ring are chamfered with the same radial slope, such thatthe clamping ring can be used either way round (upstream or downstream).Thus, when the teeth of the clamping ring come radially into contactagainst the downstream side faces of the cutouts 40, they enable theclamping ring to apply an axial force from upstream to downstream on theupstream ring 26, thereby axially clamping the upstream and downstreamrings one against the other.

Various features that are common to both of the above-describedembodiments are described below.

The resilient clamping ring 30, 30′, 30″, or 30′″ may be made in variousways. As shown in FIGS. 2 and 5, it may be open or split. Alternatively,as shown in FIGS. 6 and 7, it may be a spiral ring having overlappingangular zones. Likewise, its shape with teeth 38, 38′ could vary moregradually than that shown in the figures.

The guide device of the invention is symmetrical for the upstream ringand the downstream ring, i.e. they could be interchanged.

As shown in FIG. 1, the guide device of the invention enables sealing tobe put into place. For this purpose, the axial portion 32 of theupstream ring 26 may carry a support 48 for an abradable coating for thepurpose of co-operating with wipers 50 carried by a rotor of thecompressor.

There is no need to provide any blocking of the teeth 38, 38′ of theclamping ring 30, 30′ for the purpose of preventing them from escapingfrom the cutouts 40 formed in the upstream ring 26. In the event ofsurging, it is the entire device (upstream ring, downstream ring, andclamping ring) that moves in translation.

The invention claimed is:
 1. A device for guiding variable pitchdiffuser vanes of a turbine engine, the device comprising: a first ringhaving an axial portion at a periphery of the first ring that isextended by a collar extending radially outwards; a second ring mountedaround the axial portion of the first ring so as to cooperate therewithto define a plurality of outwardly open sockets; a plurality ofcylindrical bushings, each mounted in a respective socket for thepurpose of receiving a guide pivot of a diffuser vane; and a resilientclamping ring carrying radial teeth, for cooperating with at least oneof the first and second rings in order to clamp the first and secondrings axially one against the other, wherein the first ring or thesecond ring has a face with a profile that slopes radially, and theresilient clamping ring cooperates with said face, wherein the firstring has a plurality of angular cutouts in the axial portion of thefirst ring in order to accommodate the radial teeth carried by theclamping ring, and wherein the teeth of the clamping ring extendradially outwards and the second ring has a side face with a profilethat slopes radially.
 2. A device according to claim 1, wherein theclamping ring is designed initially to be retracted in order to passinside the first ring, and then to be released in order to enable theteeth to pass radially through the cutouts in the first ring and bearradially against the sloping side face of the second ring so as to exertan axial force clamping the two rings one against the other.
 3. A devicefor guiding variable pitch diffuser vanes of a turbine engine, thedevice comprising: a first ring having an axial portion at a peripheryof the first ring that is extended by a collar extending radiallyoutwards; a second ring mounted around the axial portion of the firstring so as to cooperate therewith to define a plurality of outwardlyopen sockets; a plurality of cylindrical bushings, each mounted in arespective socket for the purpose of receiving a guide pivot of adiffuser vane; and a resilient clamping ring carrying radial teeth, forcooperating with at least one of the first and second rings in order toclamp the first and second rings axially one against the other, whereinthe first ring or the second ring has a face with a profile that slopesradially, and the resilient clamping ring cooperates with said face,wherein the first ring has a plurality of angular cutouts in the axialportion of the first ring in order to accommodate the radial teethcarried by the clamping ring, and wherein the teeth of the clamping ringextend radially inwards, the cutouts in the first ring each having aprofile that slopes radially, and the second ring has an inwardly openannular groove.
 4. A device according to claim 3, wherein the clampingring is designed initially to be opened up to be received completelywithin the groove in the second ring, and then to be released in orderto enable the teeth to pass radially through the cutouts in the firstring and block the second ring axially in position so as to exert anaxial force clamping the two rings one against the other.
 5. A deviceaccording to claim 1, wherein the clamping ring is an open ring or aspiral ring.
 6. A device according to claim 1, wherein the first ringand the second ring include indentations for receiving the bushings. 7.A device according to claim 3, wherein the clamping ring is an open ringor a spiral ring.
 8. A device according to claim 3, wherein the firstring and the second ring include indentations for receiving thebushings.